Rahvas rock ("low brow rock", very non-literal translation) as the name of a music genre isn't exactly well established, but most people get the meaning: it's songs about activities like drinking, fucking, vomiting, passing out, farting, cruising in cars (or mopeds), and phenomena like women with big tits, women who want to have sex with you, women who don't want to have sex with you and such. Musically it's usually related to heavy metal or hard rock, sometimes to punk rock.